1. Field of the Invention
The present invention relates to an organic semiconductor device comprising a thin film transistor (TFT) using an organic semiconductor film and a process of manufacturing the same. In this specification, the organic semiconductor device denotes the device capable of functioning by utilizing the characteristics of organic semiconductor materials on the whole, that is, it refers to active matrix type semiconductor device with a TFT provided on the same substrate. Specifically, device using a luminescent element having a film containing an organic compound (hereinafter referred to as the “organic compound layer”) between a pair of electrodes, capable of obtaining the fluorescence or phosphorescence by applying an electric field thereto (hereinafter referred to as the “luminescent device”), electro-optical device such as a liquid crystal display device, electric appliances with the electro-optical device mounted as a part thereof, are also included in the range.
2. Description of the Related Art
In various kinds of semiconductor device storing a semiconductor element, such as a television image receiving device, a personal computer and a portable phone, a display for displaying characters and images is indispensable as a means for recognizing the information by a user. In particular, recently, a flat plate type display (flat panel display) represented by a liquid crystal display device, utilizing the electro-optical characteristics of the liquid crystal has been used actively.
As a form of a flat panel display, an active matrix driving method of displaying an image by providing a TFT per each pixel and successively writing a data signal, is known. The TFT serves as a prerequisite element for realizing the active matrix driving method.
Although such a TFT has been produced so far mostly utilizing an inorganic semiconductor material such as an amorphous silicon and a crystalline silicon, since the processing temperature in the manufacturing process for a semiconductor layer, or the like exceeds 350° C. in the case of forming the TFT using the material, a problem is involved in that a lot of useful substrate substances cannot be used in other cases.
In contrast, a method of producing the TFT with an organic semiconductor material has been proposed. In this specification, an organic compound showing the semiconductor-like electric property of about a 10−2 to 1016 Ωcm specific resistance is referred to as the organic semiconductor material, and a film formed with the organic semiconductor material is referred to as the organic semiconductor film. Moreover, the TFT produced using the organic semiconductor material is referred to as the organic TFT.
Since the organic TFT can be formed by the deposition method, the spin coating method, or the like of the organic semiconductor material, film formation can be enabled at a low temperature. Among the organic semiconductor materials, according to a soluble organic semiconductor material synthesized so as to be soluble in an organic solvent, coating methods such as the casting method and the spin coating method of forming a film by developing the solution on the substrate and drying can be utilized, and thus simplification of the manufacturing process can be expected. Furthermore, it is excellent in that the semiconductor film can be formed immediately without the need of the post treatment other than the drying operation.
However, in the case of forming a plurality of organic TFTs formed by a soluble organic semiconductor material, the patterning operation is difficult, and the method therefore is limited.